Hello Sergei!
It is possible. Adding silence. I don't 100% know if this does it (but
there's a second solution down there):
length of input is 10s
ecasound -i input -o output -t:15.000 [ladspa_plugin]
-t controls how long ecasound is running, if the -t value is longer than the
length of your file in seconds, there will be silence afterwards. If this
works at all, add the -t before your ladspa_plugin.
Second solution:
ecasound -i input -o output_file -t:15
ecasound output_file -o output [ladspa_plugin]
This I used myself while processing files.
Kindest regards
Julien